System and method for generating spreaded sequence with low peak-to-average power ratio (papr) waveform

ABSTRACT

Embodiments of the present disclosure relate to a method and system to generate a waveform in a communication network. The transmitter receives an input data and transmit a generated waveform to another communication system. The input data is spread with a spread code to generate a spread data and rotated using a constellation rotation operation to produce a rotated data. The rotated data is then precoded using precoding filter to produce a precoded data, and transformed into DFT output data using DFT operation. The DFT output data is then mapped with subcarriers to generate the sub-carrier mapped DFT data and modulated using Orthogonal Frequency Division Multiplexing (OFDM) modulation to generate the waveform with low PAPR.

TECHNICAL FIELD

Embodiments of the present disclosure are related, in general tocommunication, but exclusively relate to method and system forgenerating and transmitting a waveform having low peak-to-average powerratio (PAPR) data or control communication using a spread sequence.Embodiments disclose spreading sequences that have low PAPR and lowcross-correlation.

BACKGROUND

Presently, 5G new radio (NR) supports enhanced mobile broadband (eMBB),ultra-reliable-low-latency-communication (URLLC) andmassive-machine-type-communication (mMTC) for frequency bands below 6GHz, as well as above 6 GHz, including millimeter wave bands i.e. 20-40GHz and 20-30 GHz.

For ultra-low latency, a communication system requires uplink controlinformation such as hybrid automatic repeat request (ARQ) ACK/NACK, forat least one of successful decoding of block through 1-bit ACK/NACKcommands, and uplink sounding reference signal (SRS) to be sent to thebase station with very low delay. Other control information compriseschannel quality indicator (CQI), MIMO rank and other information.

As per the specifications, 5G requires a method of multiplexing control,data, and SRS signals using certain waveform. The 5G NR supports bothDiscrete Fourier Transform-spread-Orthogonal frequency-divisionmultiplexing (DFT-s-OFDM) based waveform and Orthogonalfrequency-division multiplexing (OFDM) waveform for uplink. In theuplink transmission, multiple users can simultaneously transmit controlinformation in the same time frequency resources. The users may bemultiplexed in time, frequency or code domain. The user controlinformation (UCI) may be 1 or 2 bits for the case of HARQ ACK/NACK,Scheduling Request (SR) etc., or more than 2 bits for the case of CQI,MIMO rank or other information. Generally, the control channel thatcarries 1 or 2 bits UCI is called short Physical Uplink Control Channel(PUCCH) and the one that carries more than 2 bits UCI is called longPUCCH. Similarly, the reference signals (RS) which are used for channelestimation may be multiplexed in time, frequency or code domain.Existing methods do not facilitate generation of a waveform that cantransmit the signal at or near PA saturation power level. Therefore,there exists a need for a method of transmitting UCI up to 2 bits ormore than two bits using a waveform with low PAPR so that the poweramplifier (PA) can transmit at maximum available power and that thewaveform preferably support transmission of multiple users in the sametime frequency resources.

SUMMARY

The shortcomings of the prior art are overcome and additional advantagesare provided through the provision of method of the present disclosure.

Additional features and advantages are realized through the techniquesof the present disclosure. Other embodiments and aspects of thedisclosure are described in detail herein and are considered a part ofthe claimed disclosure.

Accordingly, the present disclosure relates to a method of generating awaveform in a communication network. The method comprises performingspreading operation on an input data with a spread code to generate aspread data. The spread data is then rotated to generate a rotated datawhich is then precoded using a precoding filter to produce a precodeddata. The method further comprising transforming of precoded data intoDFT output data using DFT operation and mapped with sub-carriers togenerate a sub-carrier mapped DFT data. Upon mapping operation, thesub-carrier mapped DFT transformed data is the modulated usingOrthogonal Frequency Division Multiplexing (OFDM) to generate thewaveform.

Further, the present disclosure relates to a system for generating awaveform in a communication network. The system comprises a processor,and a memory communicatively coupled to the processor. The processor isconfigured to spread input data with a spread code to generate a spreaddata and perform a constellation rotation operation on the spread datato produce a rotated data. The processor is further configured toprecode the rotated data using a precoding filter to produce a precodeddata and perform Discrete Fourier Transform (DFT) on the precoded datato generate DFT output data. Furthermore, the processor maps the DFToutput data with one of contiguous and distributed subcarriers togenerate the sub-carrier mapped DFT data. Upon mapping of the DFT outputdata, the processor generates a waveform based on Orthogonal FrequencyDivision Multiplexing (OFDM) modulation of the sub-carrier mapped DFTdata.

In another embodiment, the present disclosure relates to a method fordetecting a waveform in a communication network. The method comprisingtransforming an input data using Discrete Fourier Transform (DFT)operation to obtain transformed data. The method further comprisingde-mapping the transformed data using sub carriers to generate ade-mapped transformed output data. Upon de-mapping operation, the methodfurther comprises step of filtering the de-mapped transformed outputdata using estimated channel information to generate OFDM symbol leveloutput. The OFDM symbol data is generated by processing the OFDM symbollevel output to remove a cover code and generate OFDM symbol data.Furthermore, the method comprising estimating at least data and controlinformation by demodulating the processed OFDM symbol data.

Further, the present disclosure relates to a system for detecting awaveform in a communication network. The system comprises a processorand a memory communicatively coupled with the processor. The processoris configured to transform input data using Discrete Fourier Transform(DFT) operation to obtain transformed data. The processor is furtherconfigured to de-map the transformed data using sub carriers to generatea de-mapped transformed output data and filter the de-mapped transformedoutput data using estimated channel information to generate OFDM symbollevel output. The processor processes the OFDM symbol level output toremove a cover code and generates OFDM symbol data. Further, theprocessor estimates at least data and control information bydemodulating the processed OFDM symbol data.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this disclosure, illustrate exemplary embodiments and, togetherwith the description, serve to explain the disclosed principles. In thefigures, the left-most digit(s) of a reference number identifies thefigure in which the reference number first appears. The same numbers areused throughout the figures to reference like features and components.Some embodiments of device or system and/or methods in accordance withembodiments of the present subject matter are now described, by way ofexample only, and with reference to the accompanying figures, in which:

FIG. 1 shows a block diagram of a communication system for transmittinga pi/2 Binary Phase Shift Keying (BPSK) spreaded and filtered sequencebased waveform, in accordance with an embodiment of the presentdisclosure;

FIGS. 2A and 2B depicts illustration of a representation of input datawith reference symbols in a communication system, in accordance with anembodiment of the present disclosure;

FIG. 2C shows an illustration of an input data, and FIG. 2D shows anillustration of spread code sequence is applied on each symbol, inaccordance with some embodiments of the present disclosure;

FIG. 2E shows a block diagram of a communication system for generatingand transmitting a waveform from a user data which is multiplexed infrequency domain, in accordance with an embodiment of the presentdisclosure;

FIG. 2F shows a block diagram of a communication system for generatingand transmitting a waveform from a user data which is multiplexed infrequency domain, in accordance with an alternative embodiment of thepresent disclosure;

FIG. 3 shows a block diagram illustration of a communication system forreceiving waveform, in accordance with an embodiment of the presentdisclosure;

FIG. 4A shows a block diagram of a communication system for receivingthe waveform, in accordance with an embodiment of the presentdisclosure;

FIG. 4B illustrates an example scenario of BSs that multiplex userequipment's, in accordance with an embodiment of the present disclosure;

FIG. 5 shows a block diagram of a communication system for receiving thewaveform in frequency domain, in accordance an embodiment of the presentdisclosure;

FIG. 6 a shows a block diagram of a communication system for receivingthe waveform with widely linear code cover, in accordance with anotherembodiment of the present disclosure;

FIG. 6 b shows a block diagram of a channel estimation module inaccordance with some embodiment of the present disclosure;

FIG. 7 shows a flowchart illustrating a method of generating waveform bya communication system, in accordance with some embodiments of thepresent disclosure; and

FIG. 8 shows a flowchart illustrating a method for detecting a waveformin a communication network, in accordance with some embodiments of thepresent disclosure.

DETAILED DESCRIPTION

In the present document, the word “exemplary” is used herein to mean“serving as an example, instance, or illustration.” Any embodiment orimplementation of the present subject matter described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiment thereof has been shown by way ofexample in the drawings and will be described in detail below. It shouldbe understood, however that it is not intended to limit the disclosureto the particular forms disclosed, but on the contrary, the disclosureis to cover all modifications, equivalents, and alternative fallingwithin the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof,are intended to cover a non-exclusive inclusion, such that a setup,device or method that comprises a list of components or steps does notinclude only those components or steps but may include other componentsor steps not expressly listed or inherent to such setup or device ormethod. In other words, one or more elements in a device or system orapparatus proceeded by “comprises . . . a” does not, without moreconstraints, preclude the existence of other elements or additionalelements in the device or system or apparatus.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the invention(s)” unless expressly specified otherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise. Theterms “a”, “an” and “the” mean “one or more”, unless expressly specifiedotherwise.

Embodiments of the present disclosure relate to a method and system togenerate a waveform in a communication network. The transmitter receivesan input data and transmit a generated waveform to another communicationsystem. The method receives the input data and spread input data with aspread code to generate a spread data and perform a constellationrotation operation on the multiplied data to produce a rotated data. Themethod further comprises precoding the rotated data using precodingfilter to produce a precoded data, and mapping the DFT output data withone of contiguous and distributed subcarriers to generate thesub-carrier mapped DFT data. Based on Orthogonal Frequency DivisionMultiplexing (OFDM) modulation of the sub-carrier mapped DFT data, thewaveform is generated.

FIG. 1 shows a block diagram of a communication system for transmittinga pi/2 Binary Phase Shift Keying (BPSK) spreaded and filtered sequencebased waveform, in accordance with an embodiment of the presentdisclosure.

As shown in FIG. 1 , the communication system 100 comprises a processor102, and memory 104 coupled with the processor 102. The communicationsystem 100 may also be referred as a transmitter. The processor 102 maybe configured to perform one or more functions of the communicationsystem 100 for receiving input data and generate waveform fortransmitting to a receiver. In one implementation, the communicationsystem 100 may comprise modules 106 for performing various operations inaccordance with the embodiments of the present disclosure. Thecommunication system 100 may be used for transmission of 1-bit or 2-bituser control information (UCI) using coherent communication or fortransmission of more than 2 bits UCI or data. Coherent communicationrefers to a system that uses a reference signal (RS) for channelestimation and demodulates the UCI or data using an estimated channel.

The modules 106 includes a spreading module 108, rotation module 110, aprecoder 112, a discrete Fourier transform (DFT) and subcarrier mappingmodule 114, an inverse fast Fourier transform (IFFT) module 116 and anoutput module 118. The discrete Fourier transform (DFT) and subcarriermapping module 114 is hereinafter referred as a DFT module 114. Theinverse DFT module 116 is also referred as an inverse Fast Fouriertransform (IFFT) module.

The spreading module 108 receives an input data 118 which may be BPSKsymbols that are spread using a spreading code to generate spread data.For example, the input data 118 may be a BPSK sequence. In anotherexample, the input BPSK sequence may be of length Q=1 for 1-bitfeedback. The technique of spreading may be generalized to transmissionof one or more than 1 bit where each hit is mapped to a BPSK symbol andis spread using a spreading code, in one embodiment. In anotherembodiment, the spreading module 108 may receive input as two bits,which may be communicated using a QPSK constellation point and furtherspread using a BPSK spreading code.

In one embodiment, the rotation module 110 receives the spread data andperforms a constellation rotation operation on the received spread data.The rotation module 108 performs j^(k) rotation on the spread data 118i.e., on the BPSK spread sequence to generate a rotated sequence. Therotated sequence is fed to the precoder 112 for pre-coding the rotatedinputs sequence. In another embodiment, the rotation module 110 receivesthe input data 118 and performs the constellation rotation operation onthe received input data 118. The spreading module 108 then receives therotated data and performs spreading operation using a spread code togenerate the spread data. The spread data is then fed to the precoder112 for pre-coding.

The precoder 112 may be one of 1+D and 1−D precoder as illustrated belowin equations (1) and (2):

H(D)=1+D  (1)

H(D)=1−D  (2)

Wherein D is a delay element. In an embodiment the precoder may be a3-tap filter of type: H(D)=0.26D⁻¹+0.92+0.26D orH(D)=−0.26D⁻¹+0.92−0.26D

In an embodiment, considering time domain, the precoder 112 represents acircular convolution of input with a two-tap filter, where the two tapshave equal values. The precoder 112 reduces PAPR of the output waveformsignificantly. The precoder 112 output is a pre-coded data, which is fedto the DFT module 114.

The DFT module 114 performs a DFT spreading and subcarrier mapping onthe precoded data, and the output of the DFT module 114 is mapped withcontiguous or distributed subcarriers for generating the transformedsequence. The DFT module 114 performs an M-point DFT operation on asequence X_(n) that may be defined as illustrated below in equation (3):

$\begin{matrix}\begin{matrix}{{X_{k} = {\sum\limits_{l = 0}^{M - 1}{x_{n}e^{\frac{{- i}2\pi{kl}}{M}}}}},} & {{k = 0},1,2,{{\ldots M} - 1}} & {i = \sqrt{- 1}}\end{matrix} & (3)\end{matrix}$

In an embodiment, considering the precoder 112 is a 1+D precoder0.26D⁻¹+0.92+0.26D, then the DFT module 114 performs a subcarriermapping such that the DFT is taken over the range 0, . . . , M−1, thenthe left half of DFT output will be swapped with right half. In anotherembodiment, if the precoder 112 is a 1−D precoder or)=−0.26D⁻¹+0.92−0.26D and if the DFT is taken over the range 0, . . . ,M−1, then the output of the DFT module 114 output will be directlymapped to one of contiguous and distributed subcarriers.

In another embodiment, the precoder 112 may be a filter with real orcomplex-values whose length is less than or equal to the DFT size. Inyet another embodiment, the precoder 112 may be alternativelyimplemented in frequency domain after the DFT as a subcarrier levelfilter. The subcarrier filter may be computed as the M-point DFT of thetime domain precoder.

In another embodiment, the DFT module 114 performs DFT spreading andsub-carrier mapping operation on the input data which is not pre-coded.The input data may be one of a rotated data and spread data. The DFTmodule 114 performs DFT operation on the input data and the output datais then pre-coded using the precoder 112.

The IDFT module 116 is configured to perform an inverse transform of thetransformed sequence, to generate a time domain signal. After the IDFTor IFFT operation, the output module 118 performs at least one ofaddition of cyclic prefix, cyclic suffix, windowing, windowing withoverlap and adding operation (WOLA) on the time domain signal togenerate output sequence 122. A half subcarrier frequency shift may beapplied to avoid DC transmission. In an embodiment, the output sequence122 may be fed to the digital to analog converter to generate an analogwaveform. The output sequence 122 is at least one of 1-bit control dataand 2-bit control data for short duration physical uplink controlchannel (PUCCH), in an embodiment. In one embodiment of 1 or 2 bit UCI,the waveform may be realized by pre-computing the values at the outputof DFT for a given spreading sequence with a reference positive BPSKinput so that the entire waveform may be specified as a sequence. Thissequence may be multiplied with a BPSK or QPSK UCI symbol beforeapplying subcarrier mapping and IDFT. This method results in a set offrequency domain sequences that are only a function of BPSK spreadingsequences. In a preferred embodiment the precoder takes 2 or 3-taps intime domain. In another embodiment, the output sequence 122 is a longPUCCH that transmit UCI or data of length more than 2 bits.

In an embodiment, the precoder 112 is not defined by standard, butimplementation specific. For such precoder 112, since RS andcontrol/data use the same precoder, the channel estimates implicitlyestimate the precoder value. In such cases, it is sufficient to specifythe BPSK spreading sequences only. In an embodiment, the communicationsystem 100 is configured to optionally multiply the subcarrier mappedDFT data with an element of Orthogonal Cover Code (OCC), when therotation on the input data is performed directly without spreading.Also, an inverse Discrete Fourier Transform (IDFT) on the subcarriermapped DFT output with OCC can be performed to generate IDFT output.Thereafter, the output module 118 generates a waveform by performingOrthogonal Frequency Division Multiplexing (OFDM) modulation.

FIGS. 2A and 2B depicts illustration of a representation of input datawith reference symbols in a communication system, in accordance withanother embodiment of the present disclosure.

As shown in FIGS. 2A and 2B, the input data may be a 1 or 2-bitdata/control information may be repeated over multiple OFDM symbolsusing a code cover. The sequence may have one subframe with controlreference symbol (RS) multiplexing in accordance with an embodiment ofthe present disclosure. The RS may be multiplexed with control usingalternating patterns with different RS density. As shown in FIG. 2A, theinput data is combination of sequence of data/control information andRS, repeated alternatively. FIG. 2B shows another embodiment of inputdata sequence, which is a combination of sequence of data/controlinformation and RS in any combination.

FIG. 2C shows an illustration of an input data. In one embodiment, theinput data is a plurality of real or complex-valued symbols. FIG. 2Dshows an illustration of spread code sequence is applied on each symbol.The spread sequence may be selected as one of BPS K, Gold sequences,m-sequences etc. The RS may use ZC sequences or BPSK sequences whereBPSK sequences or spreading codes may be obtained from Gold sequences,m-sequences or computer-generated sequences that minimize PAPR.

In another embodiment, data of multiple users is multiplexed using atleast one of time, frequency and code domain using DFT-S-OFDM that usespi/2 BPSK modulation with spectrum shaping or higher order modulation.In this embodiment, RS is time multiplexed with data or RS may occupydifferent OFDM symbols other than data. The RS of multiple users may bemultiplexed in at least one of time, code, and frequency dimensions.

FIG. 2E shows a block diagram of a communication system for generatingand transmitting a waveform from a user data which is multiplexed infrequency domain with reference signal or other user data, in accordancewith an alternative embodiment of the present disclosure.

As shown in FIG. 2E, the communication system 200 includes the processor202, and the memory 204. The memory 204 may be communicatively coupledto the processor 202. The processor 202 may be configured to perform oneor more functions of the communication system 200 for receiving data. Inone implementation, the communication system 200 may comprise modules206 for performing various operations in accordance with the embodimentsof the present disclosure. The communication system 200 is configured tomultiplex user data in frequency domain. The data may be controlinformation. The communication system 200 includes at least onetransceiver (not shown in Fig) to perform receiving an input data from atransmitter, and transmitting a generated waveform to a destination.

The modules 206 includes a modulation and rotation module 208, aprecoder 210, a discrete Fourier transform (DFT) module 212, adistributed subcarrier allocation module 214 and an output module 216.The discrete Fourier transform (DFT) 212 is also referred as DFT module.

The modulation and rotation module 208 is configured to performmodulation and rotation on the input data 218 to generate rotated data.In one embodiment, the input data 218 may be channel coded data orcontrol information bits. In another embodiment, the input data 218 isuser data. The rotation performed by the modulation and rotation module208 is constellation rotation. The modulation may be one of BPSK, QPSKand any other modulation. For BPSK modulation on the control bits 218,the constellation rotation factor is pi/2 i.e. 90-deg shift betweensuccessive BPSK symbols. For QPSK modulation on the control bits 218,the constellation rotation may be zero of pi/4. A spectrum shapingfunction may be applied.

The precoder 210 is configured to receive rotated data and generateprecoded data, also referred as filtered data. The precoder may be oneof 1+D and 1−D precoder as illustrated below in equations (1) and (2):

H(D)=1+D  (1)

H(D)=1−D  (2)

Wherein D is a delay element. In an embodiment the precoder may be a3-tap filter of type: H(D)=0.26D⁻¹+0.92+0.26D orH(D)=−0.26D⁻¹+0.92−0.26D. The precoder 210 reduces PAPR of the waveformsignificantly.

The DFT module 212 performs a DFT spreading and subcarrier mapping onthe precoded data, and the output of the DFT module 212 is mapped withcontiguous or distributed subcarriers for generating the transformedsequence. The spectrum shaping may be implemented as a circularconvolution in time domain or after DFT module 212 in frequency domainas a multiplication filter at subcarrier level. The frequency domainsubcarriers are one of localized and distributed.

The distributed subcarrier allocation module 214 is configured toreceive the precoded data and perform allocation of distributedsubcarriers which are evenly spaced with in the allocated resource blockof a length M. For example, if U users are frequency multiplexed thenthere are U−1 null tones between successive data subcarriers. In thisexample, U users may be frequency multiplexed where each user has adifferent starting position in subcarrier mapping. In an embodiment, theuser data may comprise of data or control information or referencesignal sequence.

The output module 216 is configured to perform inverse DFT or IFFT,followed by at least one of CP addition and at least one of windowing,WOLA and filtering operations to generate an output sequence 220. Theinput control bits 218 may include RS which may occupy different OFDMsymbols than data.

In an alternative embodiment, the multiple users may be multiplexed intime domain in different OFDM symbols, or a combination of time domain,frequency domain and code domain multiplexing to generate the outputsequence 220.

FIG. 2F shows a block diagram of a communication system for generatingand transmitting a waveform from a user data which is generated directlyin frequency domain, in accordance with an alternative embodiment of thepresent disclosure. This type of implementation is suitable for the casewhen 1 or 2 bit UCI is mapped to BPSK or QPSK constellation point andthe constellation point is spread using a sequence that is input to theIDFY directly thus omitting the intermediate steps of constellationrotation, precoding and DFT operation resulting in a low-complexityimplementation that requires specification or storage of possiblefrequency domain spreading sequences.

As shown in FIG. 2F, the communication system 250 includes the processor252, and the memory 254. The memory 254 may be communicatively coupledto the processor 252. The processor 252 may be configured to perform oneor more functions of the communication system 250 for receiving data. Inone implementation, the communication system 250 may comprise modules256 for performing various operations in accordance with the embodimentsof the present disclosure. The communication system 250 is configured tosend user data in frequency domain. The data may be control information.The communication system 250 includes at least one transceiver (notshown in Fig) to perform receiving an input data from a transmitter, andtransmitting a generated waveform to a destination.

The modules 256 includes a multiplication module 258, a cyclic shiftingmodule 260, an inverse discrete Fourier transform (IDFT) module 262 andan output module 264. The frequency domain module 258 receives an inputfrequency domain sequence 266 which may be obtained using a basesequence that is obtained by taking a BPSK sequence that goes throughpi/2 constellation rotation, precoding and DFT operations. Variouscyclic shifts of the base sequence may be used as inputs. The basesequences and the number of cyclic shifts that result in low PAPR andlow correlation among the base sequences and zero correlation among thecyclic shifts of a base sequence may be obtained through a computersearch. The multiplication module 258 multiplies the input frequencydomain sequence 266 with a control information carrying modulationalphabet. The modulation alphabet can be a real or complex value.

The cyclic shifting module 260 apply cyclic shifts by multiplying theelements of the frequency domain sequence 266 with a complex exponentialvalue that introduces required cyclic shift in frequency domain suchthat the cyclic shifted base sequences are orthogonal to each other. Inone example, the number of cyclic shift may be up to 6 i.e., value inthe range 0, 1, 2, 3, 4, 5. The time domain cyclic shift is a right orleft circular shift of the base sequence. The base sequences areoptimized such that the generated waveforms have optimized or low PARP.The time domain computer generated BPSK base sequences are illustratedin the below Table 1 The corresponding frequency domain base sequencesare tabulated in Table 4.

TABLE 1 S. No. Sequence 1 1 −1 −1 −1 −1 1 −1 1 −1 −1 1 1 2 −1 −1 −1 −1−1 1 1 −1 −1 1 −1 1 3 −1 −1 −1 −1 1 −1 −1 1 1 1 −1 1 4 1 −1 −1 −1 1 −1 11 1 −1 −1 1 5 −1 −1 −1 −1 1 1 −1 1 −1 −1 −1 1 6 1 −1 −1 1 −1 −1 −1 1 −11 1 −1 7 1 −1 −1 1 1 −1 1 1 1 1 −1 1 8 1 1 −1 −1 −1 1 −1 −1 −1 −1 1 1 9−1 1 −1 1 1 −1 −1 −1 −1 1 −1 −1 10 −1 1 1 −1 1 −1 1 1 1 1 1 −1 11 −1 1 11 −1 1 −1 −1 −1 −1 1 −1 12 1 −1 1 1 −1 −1 1 1 1 1 1 −1 13 −1 −1 −1 −1 1−1 −1 −1 1 −1 1 1 14 1 −1 −1 −1 1 1 −1 −1 1 −1 1 −1 15 1 −1 −1 1 −1 −1−1 −1 1 1 −1 1 16 −1 −1 −1 1 −1 −1 1 1 1 −1 1 −1 17 1 −1 −1 1 −1 1 1 1 1−1 1 1 18 −1 −1 1 −1 −1 −1 −1 1 −1 1 1 1 19 −1 −1 1−1 1 1 −1 −1 −1 −1 1−1 20 −1 −1 1 1 −1 1 −1 −1 −1 1 −1 −1 21 1 1 −1 −1 1 1 −1 −1 −1 −1 −1 122 1 −1 1 −1 −1 −1 1 1 −1 1 1 1 23 1 1 −1 1 −1 1 1 1 1 1 −1 −1 24 1 1 11 1 −1 1 −1 1 1 −1 −1 25 1 −1 −1 −1 1 −1 1 −1 −1 1 1 −1 26 −1 −1 −1 1 −11 1 −1 −1 −1 −1 1 27 1 −1 −1 1 −1 1 1 1 −1 −1 1 −1 28 1 −1 −1 1 1 −1 −11 −1 1 −1 −1 29 1 −1 −1 1 1 −1 1 −1 −1 −1 1 −1 30 1 −1 1 −1 −1 1 1 1 −11 −1 −1

Below Table 4 shows 30 sequences in frequency domain, which may bedirectly used by the BPSK or QPSK sequences.

TABLE 4 S. No DFT output 1 0.0000 + 0.0000i 1.4142 + 0.3789i 1.4142 −1.4142i −2.8284 − 2.8284i −2.4495 + 2.4495i 1.4142 + 5.2779i −2.8284 +2.8284i −5.2779 + 1.4142i 2.4495 − 2.4495i −2.8284 + 2.8284i 1.4142 −1.4142i −0.3789 + 1.4142i 2 0.0000 + 0.0000i 1.4142 + 0.3789i 0.5176 −1.9319i −2.8284 − 2.8284i −3.3461 + 0.8966i 1.4142 + 5.2779i −2.8284 −2.8284i 3.8637 + 3.8637i −0.8966 + 3.3461i −2.8284 + 2.8284i −1.9319 +0.5176i −1.0353 − 1.0353i 3 0.0000 + 0.0000i −0.1895 − 0.7071i 1.7424 −2.6390i −1.4142 − 1.4142i −4.5708 + 3.0179i −2.6390 − 0.7071i 5.6569 +2.8284i −2.6390 + 0.7071i 0.3282 + 5.4674i −1.4142 + 1.4142i −3.1566 −0.1895i −0.1895 + 0.7071i 4 0.0000 + 0.0000i 0.1895 + 0.7071i −0.1895 −3.1566i −1.4142 − 1.4142i −5.4674 − 0.3282i 2.6390 + 0.7071i 2.8284 +5.6569i −2.6390 + 0.7071i −3.0179 + 4.5708i 1.4142 − 1.4142i −2.6390 +1.7424i −0.1895 + 0.7071i 5 0.0000 + 0.0000i 1.4142 + 0.3789i −1.4142 −1.4142i −2.8284 − 2.8284i −2.4495 − 2.4495i 1.4142 + 5.2779i 2.8284 +2.8284i −5.2779 + 1.4142i 2.4495 + 2.4495i −2.8284 + 2.8284i −1.4142 −1.4142i −0.3789 + 1.4142i 6 0.0000 + 0.0000i −0.3789 − 1.4142i 1.4142 −1.4142i −2.8284 − 2.8284i −2.4495 + 2.4495i −5.2779 − 1.4142i −2.8284 +2.8284i 1.4142 − 5.2779i 2.4495 − 2.4495i −2.8284 + 2.8284i 1.4142 −1.4142i 1.4142 − 0.3789i 7 0.0000 + 0.0000i −0.1895 − 0.7071i −0.1895 −3.1566i 1.4142 + 1.4142i −5.4674 − 0.3282i −2.6390 − 0.7071i 2.8284 +5.6569i 2.6390 − 0.7071i −3.0179 + 4.5708i −1.4142 + 1.4142i −2.6390 +1.7424i 0.1895 − 0.7071i 8 0.0000 + 0.0000i 1.4142 + 0.3789i 1.4142 +1.4142i −2.8284 − 2.8284i 2.4495 + 2.4495i 1.4142 + 5.2779i −2.8284 −2.8284i −5.2779 + 1.4142i −2.4495 − 2.4495i −2.8284 + 2.8284i 1.4142 +1.4142i −0.3789 + 1.4142i 9 0.0000 + 0.0000i −0.3789 − 1.4142i −1.4142 +1.4142i −2.8284 − 2.8284i 2.4495 − 2.4495i −5.2779 − 1.4142i 2.8284 −2.8284i 1.4142 − 5.2779i −2.4495 + 2.4495i −2.8284 + 2.8284i −1.4142 +1.4142i 1.4142 − 0.3789i 10 0.0000 + 0.0000i −1.4142 − 0.3789i 0.5176 −1.9319i 2.8284 + 2.8284i −3.3461 + 0.8966i −1.4142 − 5.2779i −2.8284 −2.8284i −3.8637 − 3.8637i −0.8966 + 3.3461i 2.8284 − 2.8284i −1.9319 +0.5176i 1.0353 + 1.0353i 11 0.0000 + 0.0000i −0.1895 − 0.7071i −1.7424 +2.6390i −1.4142 − 1.4142i 4.5708 − 3.0179i −2.6390 − 0.7071i −5.6569 −2.8284i −2.6390 + 0.7071i −0.3282 − 5.4674i −1.4142 + 1.4142i 3.1566 +0.1895i −0.1895 + 0.7071i 12 0.0000 + 0.0000i −1.4142 − 0.3789i 1.4142 −1.4142i 2.8284 + 2.8284i −2.4495 + 2.4495i −1.4142 − 5.2779i −2.8284 +2.8284i 5.2779 − 1.4142i 2.4495 − 2.4495i 2.8284 − 2.8284i 1.4142 −1.4142i 0.3789 − 1.4142i 13 −0.0000 + 0.0000i 1.0353 − 1.0353i 1.9319 −0.5176i −2.8284 − 2.8284i −0.8966 + 3.3461i −3.8637 + 3.8637i 2.8284 +2.8284i −5.2779 + 1.4142i −3.346i + 0.8966i 2.8284 − 2.8284i −0.5176 +1.9319i −0.3789 + 1.4142i 14 −0.0000 + 0.0000i 1.0353 − 1.0353i −0.5176− 1.9319i −2.8284 − 2.8284i −3.3461 − 0.8966i −3.8637 + 3.8637i 2.8284 −2.8284i −5.2779 + 1.4142i −0.8966 − 3.3461i 2.8284 − 2.8284i 1.9319 +0.5176i −0.3789 + 1.4142i 15 0.0000 + 0.0000i −0.3789 − 1.4142i 1.9319 −0.5176i −2.8284 − 2.8284i −0.8966 + 3.3461i −5.2779 − 1.4142i 2.8284 +2.8284i 3.8637 + 3.8637i −3.3461 + 0.8966i −2.8284 + 2.8284i −0.5176 +1.9319i −1.0353 − 1.0353i 16 0.0000 + 0.0000i −0.7071 − 0.1895i 0.1895 −3.1566i −1.4142 − 1.4142i −5.4674 + 0.3282i −0.7071 − 2.6390i −2.8284 +5.6569i 0.7071 − 2.6390i −3.0179 − 4.5708i 1.4142 − 1.4142i 2.6390 +1.7424i 0.7071 − 0.1895i 17 0.0000 + 0.0000i 0.7071 + 0.1895i 0.1895 −3.1566i 1.4142 + 1.4142i −5.4674 + 0.3282i 0.7071 + 2.6390i −2.8284 +5.6569i −0.7071 + 2.6390i −3.0179 − 4.5708i −1.4142 + 1.4142i 2.6390 +1.7424i −0.7071 + 0.1895i 18 0.0000 + 0.0000i −0.1895 − 0.7071i 3.1566 −0.1895i −1.4142 − 1.4142i −0.3282 + 5.4674i −2.6390 − 0.7071i −5.6569 +2.8284i −2.6390 + 0.7071i 4.5708 + 3.0179i −1.4142 + 1.4142i −1.7424 −2.6390i −0.1895 + 0.7071i 19 0.0000 + 0.0000i 1.0353 − 1.0353i −1.9319 +0.5176i −2.8284 − 2.8284i 0.8966 − 3.3461i −3.8637 + 3.8637i −2.8284 −2.8284i −5.2779 + 1.4142i 3.3461 − 0.8966i 2.8284 − 2.8284i 0.5176 −1.9319i −0.3789 + 1.4142i 20 0.0000 − 0.0000i −0.3789 − 1.4142i−1.9319 + 0.5176i −2.8284 − 2.8284i 0.8966 − 3.3461i −5.2779 − 1.4142i−2.8284 − 2.8284i 3.8637 + 3.8637i 3.3461 − 0.8966i −2.8284 + 2.8284i0.5176 − 1.9319i −1.0353 − 1.0353i 21 0.0000 + 0.0000i 1.4142 + 0.3789i−1.4142 + 1.4142i −2.8284 − 2.8284i 2.4495 − 2.4495i 1.4142 + 5.2779i2.8284 − 2.8284i −5.2779 + 1.4142i −2.4495 + 2.4495i −2.8284 + 2.8284i−1.4142 + 1.4142i −0.3789 + 1.4142i 22 0.0000 + 0.0000i 0.1895 + 0.7071i3.1566 − 0.1895i 1.4142 + 1.4142i −0.3282 + 5.4674i 2.6390 + 0.7071i−5.6569 + 2.8284i 2.6390 − 0.7071i 4.5708 + 3.0179i 1.4142 − 1.4142.i−1.7424 − 2.6390i 0.1895 − 0.7071i 23 −0.0000 + 0.0000i −1.0353 +1.0353i −0.5176 − 1.9319i 2.8284 + 2.8284i −3.3461 − 0.8966i 3.8637 −3.8637i 2.8284 − 2.8284i 5.2779 − 1.4142i −0.8966 − 3.3461i −2.8284 +2.8284i 1.9319 + 0.5176i 0.3789 − 1.4142i 24 0.0000 + 0.0000i −1.4142 −0.3789i −1.4142 + 1.4142i 2.8284 + 2.8284i 2.4495 − 2.4495i −1.4142 −5.2779i 2.8284 − 2.8284i 5.2779 − 1.4142i −2.4495 + 2.4495i 2.8284 −2.8284i −1.4142 + 1.4142i 0.3789 − 1.4142i 25 0.0000 + 0.0000i 1.0353 −1.0353i 0.5176 − 1.9319i −2.8284 − 2.8284i −3.3461 + 0.8966i −3.8637 +3.8637i −2.8284 − 2.8284i 1.4142 − 5.2779i −0.8966 + 3.3461i 2.8284 −2.8284i −1.9319 + 0.5176i 1.4142 − 0.3789i 26 0.0000 + 0.0000i 1.4142 +0.3789i −1.9319 − 0.5176i −2.8284 − 2.8284i −0.8966 − 3.3461i 1.4142 +5.2779i −2.8284 + 2.8284i 3.8637 + 3.8637i −3.3461 − 0.8966i − 2.8284 +2.8284i 0.5176 + 1.9319i −1.0353 − 1.0353i 27 0.0000 + 0.0000i 0.7071 +0.1895i −1.7424 − 2.6390i −1.4142 − 1.4142i −4.5708 − 3.0179i 0.7071 +2.6390i −5.6569 + 2.8284i 0.7071 − 2.6390i 0.3282 − 5.4674i −1.4142 +1.4142i 3.1566 − 0.1895i 0.7071 − 0.1895i 28 0.0000 + 0.0000i −0.3789 −1.4142i −1.4142 − 1.4142i −2.8284 − 2.8284i −2.4495 − 2.4495i −5.2779 −1.4142i 2.8284 + 2.8284i 1.4142 − 5.2779i 2.4495 + 2.4495i −2.8284 +2.8284i −1.4142 − 1.4142i 1.4142 − 0.3789i 29 0.0000 + 0.0000i 1.0353 −1.0353i −1.9319 − 0.5176i −2.8284 − 2.8284i −0.8966 − 3.3461i −3.8637 +3.8637i −2.8284 + 2.8284i 1.4142 − 5.2779i −3.3461 − 0.8966i 2.8284 −2.8284i 0.5176 + 1.9319i 1.4142 − 0.3789i 30 0.0000 + 0.0000i −0.5176 +0.5176i −1.4142 − 2.8284i −1.4142 − 1.4142i −4.8990 − 2.4495i 1.9319 −1.9319i −5.6569 − 2.8284i 1.9319 + 1.9319i 4.8990 + 2.4495i −1.4142 +1.4142i −1.4142 − 2.8284i −0.5176 − 0.5176i

The IDFT module 262 is configured to perform inverse DFT or IFFT of thecyclic shifted frequency domain sequence to generate IDFT data.Thereafter, the output module 264 performs one of CP addition and atleast one of windowing, WOLA and filtering operations to generate anoutput sequence 268.

FIG. 3 shows a block diagram illustration of a communication system 300for receiving waveform, in accordance with an embodiment of the presentdisclosure.

As shown in FIG. 3 , the communication system 300 includes a processor302, and memory 304. The communication system 300 is also referred as areceiver. The memory 304 may be communicatively coupled to the processor302. The processor 302 may be configured to perform one or morefunctions of the receiver 300 for receiving data. In one implementation,the receiver 300 may comprise modules 306 for performing variousoperations in accordance with the embodiments of the present disclosure.

The modules 306 includes a discrete Fourier Transform (DFT) module 310,a subcarrier de-mapping module 312, a channel estimation module 314, anequalizer module 316, an inverse discrete Fourier Transform (IDFT) 318,a De-spreading/Demodulation module 320 and a collection module 322.

The DFT module 310 is also referred as fast Fourier Transform (FFT)module. The DFT module 310 is configured to perform a DFT/FFT operationof the input data 324 to generate transformed data.

The subcarrier de-mapping module 312 performs the de-mapping operationon the transformed data, to collect allocated subcarriers. The channelestimation module 314 performs estimation of channel through which thereceiver 300 receives the input data 324. After performing the channelestimation, the equalizer module 316 performs equalization ofconstellation de-rotated data. In another embodiment, when thetransmitter uses pi/2 BPSK sequences, the equalizer module 316 is awidely linear equalizer module for filtering the de-mapped transformedoutput data is performed using a widely linear equalizer to generatefiltered data by removing effects associated with physical channel andthe precoder in the communication network.

The IDFT module 318 performs inverse Fourier transformation of equalizeddata and then followed by demodulation or soft demodulation on thetransformed data using the De-spreading module 320 to generate de-spreaddata. Thereafter, the collection module 322 collects the data de-spreaddata, thereby identifying the received input data.

FIG. 4A shows a block diagram illustration of a communication system, inaccordance with an embodiment of the present disclosure.

As shown in FIG. 4A, the communication system 400 includes a processor402, and memory 404. The communication system 400 is also referred as areceiver. The memory 404 may be communicatively coupled to the processor402. The processor 402 may be configured to perform one or morefunctions of the receiver 400 for receiving data. In one implementation,the receiver 400 may comprise modules 406 for performing variousoperations in accordance with the embodiments of the present disclosure.

The modules 406 includes processing modules 408-1, 408-2, equalizermodules 410-1, 410-2, De-spreading modules 412-1, 412-2, code coverremoval modules 414-1, 414-2, summation module 416 and de modulationmodules 418.

Each processing module 408-1, 408-2 comprises a discrete Fouriertransform (DFT) module, also referred as a fast Fourier Transform (FFT)modules, subcarrier de-mapping module, and channel estimation module.The DFT module is configured to perform a DFT/FFT operation of the inputdata 422-1, 422-2. The subcarrier de-mapping module performs thede-mapping operation on the transformed data, to collect allocatedsubcarriers. The channel estimation module performs estimation of achannel through which the receiver 400 receives the data.

After performing the channel estimation, the equalizer modules 410-1,410-2 performs equalization, to generate equalized data. Thede-spreading modules 412-1, 412-2 performs respective de-spreading togenerate corresponding de-spread data. The code cover removal modules414-1, 414-2 removes the code cover from the de-spread data to generatecorresponding data without code cover. The summation module 416 combinesthe de-spread data without code cover to generate combined data. Thedemodulation module 418 identifies the input data by demodulating thecombined data to generate an output sequence.

In an embodiment for short PUCCH transmission using 1 or 2 bit UCI andBPSK spreading of BPSK/QPSK UCI constellation points (UCI is mapped toBPSK or QPSK), considering signaling from a base station (BS) i.e. atransmitter, which is any of the communication systems 100, 200 to userequipment (UE), which is a receiver 300, 400. A code, also referred assequence, allocation is performed across plurality of BSs, also referredas multiple sectors or BSs, to reduce interference. The BSs 100 and 200may use a combination of code allocation and different frequencyresources to the users to reduce interference. Let an input sequencefrom a BS 100 and 200, be a BPSK sequence which is communicated to a UE300, 400 through two indices, first index and second index. The firstindex may indicate cell/BS specific index and second index is a shift.In an embodiment, there may be N base sequences and L shifts. Uponallocation of a base sequence by the BS 100, and 200 to the UE 300, 400,that is determined by an index, wherein the index values may be 1, 2, .. . , N, the BPSK code cover may be obtained by shifting the basesequence circularly with a shift that is indicated to the UE. The shiftmay take one of L values.

One embodiment of the present disclosure is user multiplexing i.e. 1 or2-bit control information may be transmitted over multiple OFDM symbolswhile code multiplexing multiple user using the communication system100, 200. Let C (i, j) denote a length M code where M is the occupiesnumber of subcarriers, for example M=12. The index i is the first index(base sequence index) that takes values 1, 2, . . . , N and index j isthe second index that indicates a shift applied to base sequence thattakes values in the range j=1, 2, . . . , L. In an embodiment, thecommunication 100, 200 is a base station (BS), which may multiplex usersin the same time frequency resources i.e. M subcarriers of an OFDMsymbols by assigning different values of i and j among users. The valuesof i and j may be chosen such that allocated sequences are orthogonalbetween multiplex users. The BS may assign same value of first index toall multiplexed users but different values of j (shifts) in one OFDMsymbols. For example, the maximum number of multiplexed users is 6.

In one embodiment, the BS 100, 200 may use a code cover across multipleOFDM symbols to increase multiplexing capacity. For example, first andsecond indices, having same value, may be assigned to a group ofmultiplexed users. However, user's data may be separated at the receiverby using an orthogonal code cover that is a sequence where elements ofthe sequence are multiplexed with a control signal occupied in the OFDMsymbols, where users are time multiplexed. The orthogonal code cover maybe Walsh Hadamard sequence or DFT sequence. Similarly, if multiple usersare multiplexed on the same time frequency resource, the RS occupied bythe users over multiple OFDM symbols are designed to be orthogonalsequences across multiplexed users. Orthogonality may be achieved by asequence within OFDM symbols or across OFDM symbols. For example, incase of ZC sequences, different shifts may be used across RS of OFDMsymbols. If same shift is used across multiple OFDM symbols, then anorthogonal code cover is used to separate multiple users who aremultiplexed on the same resources.

In an embodiment, a combination of the first shift, second shift (cyclicshift) and orthogonal code cover may be used for the control informationthat is spread across multiple OFDM symbols to reduce interferencecaused by co-channel control transmissions that occur in othercells/BSs. A scheduler (not shown in Fig.) configured in the BS maycoordinate through allocation of appropriate indices and code covers.

In an embodiment, considering user multiplexing capacity is less than 6,a BS may multiplex less than 6 users on the same resource. In such ascenario, the available second indices (shifts) may be used in othercells/BSs. More specifically, two or three adjacent sectors may use thesame first index (base sequence) and distinct second indices (shifts) sothat control transmissions across three sectors are orthogonal in threesectors. This may be achieved by assigning same first index of basesequence to all three sectors and further allocate shifts (1,2) in firstsector, shifts (3,4) in second sector and shifts (5,6) in another sectorwhere each sector multiplexes two users in the same OFDM symbols. FIG.4B illustrates an example scenario of BSs that multiplex userequipment's, in accordance with an embodiment of the present disclosure.

As shown in FIG. 4B, in a communication network 450, considering a firstBS 452-1 and a second BS 452-2 each with three sectors. A scheduler mayallocate different first indices or different base sequences, to thefirst BS 452-1 and the second BS 452-2 so that sequences allocated havevery low cross correlation i.e. including zero cross correlation betweencodes allocates users of first BS 452-1 and second BS 452-2.

In an embodiment, the above base sequences may be used as RS withoutmultiplying with BPSK or QPSK control information. Alternatively, ZCsequences may be used for RS. In an embodiment, a pool of base sequencesshown in Set 2 may be used.

In another embodiment, neighbouring sectors may allocate same basesequence and allocate a reduced number of shifts for user multiplexing.For example, if each sector multiplexes a maximum of two users in oneOFDM symbol, then each sector may use 2 out of 6 shifts of a basesequence such that three sectors have six users using 6 different shiftsresulting interference free communications between the six users locatedin a BS (3-sectors). This embodiment may be extended to other BS usingremaining base sequences.

In an embodiment, multiplexing capacity in a sector may be increasedmore than 6 per base sequence by repeating the control information inmultiple OFDM symbols and using OFDM symbol specific code cover orfurther spreading code over OFDM symbols. Similarly, multiplexing may beused for RS design to increase user multiplexing.

In an embodiment where the user communication control or data using aspreading sequence, the BS does not signal or indicate the spreadingsequence to the user, the user may choose one of the available set ofspreading sequences specified by the base sequences and/or the cyclicshift. The user may randomly choose either the base sequence or a shiftor both. The base station receiver would have to decode all possiblespreading sequences characterized by the base sequences and/or cyclicshifts in order to determine the set of spreading sequences used, andalso the information carried by the users.

FIG. 5 shows a block diagram of a communication system for receiving thewaveform in frequency domain, in accordance an embodiment of the presentdisclosure.

As shown in FIG. 5 , a communication system 500 includes a processor502, and memory 504. The communication system 500 is also referred as areceiver. The memory 504 may be communicatively coupled to the processor502. The processor 502 may be configured to perform one or morefunctions of the receiver 500 for receiving data. In one implementation,the receiver 500 may comprise modules 506 for performing variousoperations in accordance with the embodiments of the present disclosure.

The modules 506 includes a discrete Fourier Transform (DFT) module 508,subcarrier de-mapping module 510, matched filter 512, a channelestimation module 514, orthogonal code cover (OCC) removal module 516,and a decoder module 518. The DFT module is also referred as a fastFourier Transform (FFT) module.

In one embodiment, the DFT module 508 receives the input data 520, andperforms DFT/FFT operation of the input data 520. The subcarrierde-mapping module 510 receives the output data from the DFT module 508and performs sub-carrier de-mapping to generate the de-mapped outputi.e., frequency domain sequence which is matched filtered by the matchedfilter 512 using the estimated channel and the frequency domainsequence. The estimated channel is provided by the channel estimationmodule 514. The matched filter 512 performs multiplication with thecomplex conjugate of the estimated channel and frequency domain sequenceat each subcarrier.

In the presence of multiple receiver antennas, the matched filter 512 isfirst applied with estimated channels of each receiver antenna andoutputs of these multi-antenna antenna matched filters are combined toobtain channel matched filter output followed by another matchedfiltering with frequency domain sequence. Thereafter, the resultingoutput is summed over all available subcarriers to obtain an OFDM symbollevel output. The OCC removal module 516 removes the OCC by multiplyingthis OFDM symbol level output with complex conjugate of the OCC used forthat OFDM symbol, then sum over multiple OFDM symbols with OCC to obtaina decision variable. The decoder 518 is configured to decode thedecision variable using one of BPSK and QPSK demodulator to identify theinput data 520. This type of receiver is useful for the case where usercommunicated 1 or 2 bit UCI using BPSK or QPSK modulation alphabet.

FIG. 6 shows a block diagram of a communication system for receiving thewaveform with widely linear receiver, in accordance with anotherembodiment of the present disclosure.

As shown in FIG. 6 , a communication system 600 includes a processor602, and memory 604. The communication system 600 is also referred as areceiver. The memory 604 may be communicatively coupled to the processor602. The processor 602 may be configured to perform one or morefunctions of the receiver 600 for receiving data. In one implementation,the receiver 600 may comprise modules 606 for performing variousoperations in accordance with the embodiments of the present disclosure.

The modules 606 includes a discrete Fourier Transform (DFT) module 608,subcarrier de-mapping module 610, matched filter 612, a channelestimation module 614, frequency shifting module 616, combining module618, code matched filter 620, and orthogonal code cover (OCC) removalmodule 622. The DFT module 608 is also referred as a fast FourierTransform (FFT) module.

In one embodiment, the DFT module 608 receives the input data 624, andperforms DFT/FFT operation of the input data 624. The subcarrierde-mapping module 610 receives the output data from the DFT module 608and performs sub-carrier de-mapping to generate a de-mapped data. Thechannel matched filter 612 performs multiplication of de-mapped datawith the complex conjugate of the estimated channel at each subcarrier.In the presence of multiple receiver antennas, the matched filter isfirst applied with estimated channels of each receiver antenna andoutputs of these multi-antenna matched filters are combined to obtainchannel matched filter output.

The frequency shifting module 616 performs circular shift on each of theoutput of channel matched filter to remove pi/2 constellation by a valueM/4 on. The combining module 618 is configured to sum thefrequency-shifted output and corresponding complex-conjugated, andfrequency revered of the frequency shifted output to obtain a summedoutput. Thereafter, the code matched filter 620 multiplying eachsubcarrier of summed output with a DFT of the BPSK input sequence, andperform summation over all available subcarriers, to obtain an OFDMsymbol level output. The OCC removal module 622 removes the OCC bymultiplying the OFDM symbol level output with complex conjugate of OCCused for that OFDM symbol, then sum over multiple OFDM symbols with OCCto obtain a decision variable. A demodulator (not shown in FIG. 6 )demodulates the decision variable using BPSK or QPSK demodulator toobtain an output data 626, which is the received input data 624.

FIG. 6 b shows a block diagram of a channel estimation module inaccordance with some embodiment of the present disclosure.

As illustrated, the channel estimation module 614 comprises one or moreblocks including an FFT module 658, a sub-carrier de-mapping module 660,a channel state information estimation module (CSI estimation module)662 and a combining module 664. In one embodiment, RS samples 666 arecollected as input to the channel estimation module 614 from multipleOFDM symbols carrying RS. The FFT module 658 performs FFT operation oneach RS OFDM symbol sample to generate RS OFDM FFT sample. Thesub-carrier de-mapping module 660 collect RS sub-carrier throughsub-carrier de-mapping operation. The CSI estimation module 662determines RS channel state information using knowledge of RS and OCCfor that symbol. In one aspect, the OCC may be received from BS. Thecombining module 664 combines or interpolates the RS channel stateinformation of multiple RS OFDM symbols to generate the channel stateinformation of the RS samples and provide the generated channel stateinformation to the filter modules for further processing.

FIG. 7 shows a flowchart illustrating a method of generating waveform bya communication system, in accordance with some embodiments of thepresent disclosure.

As illustrated in FIG. 7 , the method 700 comprises one or more blocksfor generating waveform by a communication system. The method 700 may bedescribed in the general context of computer executable instructions.Generally, computer executable instructions can include routines,programs, objects, components, data structures, procedures, modules, andfunctions, which perform functions or implement abstract data types.

The order in which the method 700 is described is not intended to beconstrued as a limitation, and any number of the described method blockscan be combined in any order to implement the method. Additionally,individual blocks may be deleted from the methods without departing fromthe spirit and scope of the subject matter described herein.Furthermore, the method can be implemented in any suitable hardware,software, firmware, or combination thereof.

At block 710, an input data is processed by spreading operation using aspread code to generate spread data. In one embodiment, the spreadingmodule 108 receives an input data 118 which may be BPSK symbols that arespread using a spreading code to generate spread data. For example, theinput data 118 may be a BPSK sequence. In another example, the inputBPSK sequence may be of length Q=1 for 1-bit feedback. In anotherembodiment, the spreading module 108 may receive input as two bits,which may be communicated using a QPSK constellation point and furtherspread using a BPSK spreading code.

At block 720, a rotation operation on the multiplied data is performedto produce a rotated data. In one embodiment, the rotation module 110receives the spread data and performs a constellation rotation operationon the received spread data. The rotation module 108 performs j^(k)rotation on the spread data 118 i.e., on the BPSK spread sequence togenerate a rotated sequence. The rotated sequence is fed to the precoder112 for pre-coding the rotated inputs sequence.

At block 730, the rotated data is precoded using a precoding filter toproduce a precoded data. In one embodiment, the precoding filter is oneof 1+D precoder and 1−D precoder. In an embodiment, considering timedomain, the precoder 112 represents a circular convolution of input witha two-tap filter, where the two taps have equal values. The precoder 112reduces PAPR of the output waveform significantly. The precoder 112output is a pre-coded data, which is fed to the DFT module 114.

At block 740, DFT operation is performed on the precoded data togenerate DFT output data. At block 750, mapping of DFT output data isperformed to generate sub-carrier mapped DFT data. In one embodiment,the DFT module 114 performs a DFT spreading and subcarrier mapping onthe precoded data, and the output of the DFT module 114 is mapped withcontiguous or distributed subcarriers for generating the transformedsequence. In an embodiment, considering the precoder 112 is a 1+Dprecoder, then the DFT module 114 performs a subcarrier mapping suchthat the DFT is taken over the range 0, . . . , M−1, then the left halfof DFT output will be swapped with right half. In another embodiment, ifthe precoder 112 is a 1-D precoder and if the DFT is taken over therange 0, . . . , M−1, then the output of the DFT module 114 output willbe directly mapped to one of contiguous and distributed subcarriers.

In another embodiment, the precoder may be a filter with real orcomplex-values whose length is less than or equal to the DFT size. Inyet another embodiment, the precoder may be alternatively implemented infrequency domain after the DFT as a subcarrier level filter. The saidsubcarrier filter may be computed as the M-point DFT of the time domainprecoder.

At block 760, waveform with low PAPR is generated. In one embodiment,the IDFT module 116 is configured to perform an inverse transform of thetransformed sequence, to generate a time domain signal. After the IDFTor IFFT operation, the output module 118 performs at least one ofaddition of cyclic prefix, cyclic suffix, windowing, windowing withoverlap and adding operation (WOLA) on the time domain signal togenerate output sequence 122. A half subcarrier frequency shift may beapplied to avoid DC transmission. In an embodiment, the output sequence122 may be fed to the digital to analog converter to generate an analogwaveform. The output sequence 122 is at least one of 1-bit control dataand 2-bit control data for short duration physical uplink controlchannel (PUCCH), in an embodiment. In one embodiment of 1 or 2 bit UCI,the waveform may be realized by pre-computing the values at the outputof DFT for a given spreading sequence with a reference positive BPSKinput so that the entire waveform may be specified as a sequence. Thissequence may be multiplied with a BPSK or QPSK UCI symbol beforeapplying subcarrier mapping and IDFT. This method results in a set offrequency domain sequences that are only a function of BPSK spreadingsequences. In a preferred embodiment the precoder takes 2 or 3-taps intime domain. In another embodiment, the output sequence 122 is a longPUCCH that transmit UCI of length more than 2 bits.

FIG. 8 shows a flowchart illustrating a method of detecting waveform bya communication system, in accordance with some embodiments of thepresent disclosure.

As illustrated in FIG. 8 , the method 800 comprises one or more blocksfor detecting waveform by a communication system. The method 800 may bedescribed in the general context of computer executable instructions.Generally, computer executable instructions can include routines,programs, objects, components, data structures, procedures, modules, andfunctions, which perform functions or implement abstract data types.

The order in which the method 800 is described is not intended to beconstrued as a limitation, and any number of the described method blockscan be combined in any order to implement the method. Additionally,individual blocks may be deleted from the methods without departing fromthe spirit and scope of the subject matter described herein.Furthermore, the method can be implemented in any suitable hardware,software, firmware, or combination thereof.

At block 810, an input data is transformed using DFT. In one embodiment,the DFT module 508 receives the input data 520, and performs DFT/FFToperation of the input data 520.

At block 820, the transformed input data is de-mapped using sub-carrier.The subcarrier de-mapping module 510 receives the output data from theDFT module 508 and performs sub-carrier de-mapping to generate thede-mapped output i.e., frequency domain sequence.

At block 830, the de-mapped transformed data is filtered. In oneembodiment, the frequency domain sequence is matched filtered by thematched filter 512 using the estimated channel and the frequency domainsequence. The estimated channel is provided by the channel estimationmodule 514. The matched filter 512 performs multiplication with thecomplex conjugate of the estimated channel and frequency domain sequenceat each subcarrier. In the presence of multiple receiver antennas, thematched filter 512 is first applied with estimated channels of eachreceiver antenna.

At block 840, the OFDM symbol level output is processed. In oneembodiment, the outputs of these multi-antenna antenna matched filtersare combined to obtain channel matched filter output followed by anothermatched filtering with frequency domain sequence. Thereafter, theresulting output is summed over all available subcarriers to obtain anOFDM symbol level output. The OCC removal module 516 removes the OCC bymultiplying this OFDM symbol level output with complex conjugate of theOCC used for that OFDM symbol, then sum over multiple OFDM symbols withOCC to obtain a decision variable.

At block 850, data and control information are estimated. The decoder518 is configured to decode the decision variable using one of BPSK andQPSK demodulator to identify the input data 520.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the inventive subject matter.It is therefore intended that the scope of the invention be limited notby this detailed description. Accordingly, the disclosure of theembodiments of the invention is intended to be illustrative, but notlimiting, of the scope of the invention.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting.

What is claimed is: 1-51. (canceled)
 52. A method for generating awaveform, the method comprising: generating, via one or moretransmitters, a plurality of complex-valued baseband symbols, wherein:the plurality of complex-valued baseband symbols comprises at least onedata symbol, at least one control information symbol and at least onereference signal (RS) symbol, the generating of the plurality ofcomplex-valued baseband symbols comprises π/2 Binary Phase Shift Keying(BPSK) modulation, the generating of the plurality of complex-valuedbaseband symbols comprises converting from a time domain to a frequencydomain using a Discrete Fourier Transform (DFT), the generating of theplurality of complex-valued baseband symbols comprises basebandfiltering, the generating of the plurality of complex-valued basebandsymbols comprises mapping using Orthogonal Frequency DivisionMultiplexing (OFDM), the mapping comprises a distributed subcarriermapping of the at least one RS symbol, the distributed subcarriermapping comprises occupied subcarriers and one or more null subcarriers,the mapping comprises a localized subcarrier mapping of the at least onedata symbol and/or the at least one control information symbol, and thelocalized subcarrier mapping does not comprises a null subcarrier; andperforming time multiplexing, via the one or more transmitters, of theat least one data symbol, the at least one control information symboland the at least one RS symbol over a time period to generate thewaveform.
 53. The method as claimed in claim 52, wherein basebandfiltering occurs in the time domain.
 54. The method as claimed in claim52, wherein baseband filtering occurs in the frequency domain.
 55. Themethod as claimed in claim 52, wherein each of the plurality ofcomplex-valued baseband symbols is spectrally shaped in one of timedomain and frequency domain.
 56. The method as claimed in claim 52,wherein each of the plurality of complex-valued baseband symbolsgenerated by the one or more transmitters is a π/2 BPSK DFT-spread-OFDMsymbol.
 57. The method as claimed in claim 52, wherein the data symbolcomprises an Orthogonal Cover Code (OCC).
 58. The method as claimed inclaim 52, wherein each of the plurality of complex-valued basebandsymbols comprises control information with a spreading sequence.
 59. Themethod as claimed in claim 52, wherein the control information comprisesan OCC.
 60. The method as claimed in claim 52, wherein each of theplurality of complex-valued baseband symbols comprises an RS based on aspreading sequence.
 61. The method as claimed in claim 52, wherein eachof the one or more transmitters is associated with a different circularshifted version of the base sequence.
 62. The method as claimed in claim52, wherein each of the one or more transmitters is associated with aspreading sequence that is orthogonal to each other spreading sequenceassociated with the one or more transmitters.
 63. The method as claimedin claim 52, wherein the RS comprises an OCC.
 64. The method as claimedin claim 52, wherein at least one of a spreading sequence and an OCC isassociated with at least one of a transmitter and an OFDM symbol number.65. The method as claimed in claim 52, wherein a transmitter isassociated with at least one of a BS specific index and a sectorspecific index.
 66. The method as claimed in claim 52, wherein thecommunication network signals at least one spreading sequence and an OCCto the one or more transmitters.
 67. The method as claimed in claim 52,wherein the data symbols are filtered and the RS symbols are notfiltered.
 68. The method as claimed in claim 52, wherein the RS and thedata are spectrally shaped using the same filter.
 69. The method asclaimed in claim 52, wherein the filter comprises coefficients that area function of one of the three sequences [1], [1 1] and [0.26 0.920.26].
 70. The method as claimed in claim 52, wherein the generating ofthe plurality of complex-valued baseband symbols comprises spreading bya spreading sequence.
 71. The method as claimed in claim 70, wherein thespreading sequence is a result of cyclically shifting a base sequence.72. The method as claimed in claim 52, wherein the baseband filteringlowers a peak-to-average power ratio (PAPR).
 73. The method as claimedin claim 52, wherein the baseband filtering is applied after themapping.
 74. A transmitter, the transmitter comprises: a modulatoroperable to add π/2 Binary Phase Shift Keying (BPSK) modulation to aplurality of complex-valued baseband symbols, wherein the plurality ofcomplex-valued baseband symbols comprises at least one data symbol, atleast one control information symbol and at least one reference signal(RS) symbol; a Discrete Fourier Transform (DFT) operable to convert theplurality of complex-valued baseband symbols from a time domain to afrequency domain; a baseband filter operable to spectrally shape theplurality of complex-valued baseband symbols; and a subcarrier mapperoperable to map the plurality of complex-valued baseband symbols usingOrthogonal Frequency Division Multiplexing (OFDM), wherein: the mappingcomprises a distributed subcarrier mapping of the at least one RSsymbol, the distributed subcarrier mapping comprises occupiedsubcarriers and one or more null subcarriers, the mapping comprises alocalized subcarrier mapping of the at least one data symbol and/or theat least one control information symbol, and the localized subcarriermapping does not comprises a null subcarrier; and a time multiplexoroperable to multiplex the at least one data symbol, the at least onecontrol information symbol and the at least one RS symbol over a timeperiod to generate the waveform.
 75. The transmitter of claim 74,wherein baseband filter is applied in the time domain.
 76. Thetransmitter of claim 74, wherein baseband filter is applied in thefrequency domain.
 77. The transmitter of claim 74, wherein each of theplurality of complex-valued baseband symbols is spectrally shaped in oneof time domain and frequency domain.
 78. The transmitter of claim 74,wherein each of the plurality of complex-valued baseband symbolsgenerated by the transmitter is a π/2 BPSK DFT-spread-OFDM symbol. 79.The transmitter of claim 74, wherein the data symbol comprises anOrthogonal Cover Code (OCC).
 80. The transmitter of claim 74, whereineach of the plurality of complex-valued baseband symbols comprisescontrol information with a spreading sequence.
 81. The transmitter ofclaim 74, wherein the control information symbol comprises an OCC. 82.The transmitter of claim 74, wherein each of the plurality ofcomplex-valued baseband symbols comprises an RS based on a spreadingsequence.
 83. The transmitter of claim 74, wherein the transmitter isassociated with a unique circular shifted version of the base sequence.84. The transmitter of claim 74, wherein the transmitter is associatedwith a spreading sequence that is orthogonal to each other spreadingsequence associated with one or more other transmitters.
 85. Thetransmitter of claim 74, wherein the RS comprises an OCC.
 86. Thetransmitter of claim 74, wherein at least one of a spreading sequenceand an OCC is associated with the transmitter and an OFDM symbol number.87. The transmitter of claim 74, wherein the transmitter is associatedwith at least one of a BS specific index and a sector specific index.88. The transmitter of claim 74, wherein a communication network signalsat least one spreading sequence and an OCC to the transmitter.
 89. Thetransmitter of claim 74, wherein the data symbols are filtered and theRS symbols are not filtered.
 90. The transmitter of claim 74, whereinthe RS and the data are spectrally shaped using the same filter.
 91. Thetransmitter of claim 74, wherein the baseband filter comprisescoefficients that are a function of one of the three sequences [1], [11] and [0.26 0.92 0.26].
 92. The transmitter as claimed in claim 74,wherein the transmitter comprises a spreader operable to spread theplurality of complex-valued baseband symbols by a spreading sequence.93. The transmitter as claimed in claim 92, wherein the spreadingsequence results from cyclically shifting a base sequence.
 94. Thetransmitter as claimed in claim 74, wherein the baseband filter isconfigured to lower a peak-to-average power ratio (PAPR).
 95. Thetransmitter as claimed in claim 74, wherein the baseband filter isapplied after the subcarrier mapper.
 96. A method for processing awaveform, the method comprising: performing time de-multiplexing of anOrthogonal Frequency Division Multiplexing (OFDM) waveform, via the oneor more receivers, to generate a plurality of complex-valued basebandsymbols comprising at least one data symbol, at least one controlinformation symbol and at least one RS symbol; de-mapping the pluralityof complex-valued baseband symbols, wherein: the at least one RS symbolis mapped according to a distributed subcarrier mapping, the distributedsubcarrier mapping comprises occupied subcarriers and one or more nullsubcarriers, the at least one data symbol and/or the at least onecontrol information symbol is mapped according to a localized subcarriermapping, and the localized subcarrier mapping does not comprises a nullsubcarrier; converting from frequency domain symbols to time domainsymbols using an Inverse Discrete Fourier Transform (IDFT); andperforming π/2 Binary Phase Shift Keying (BPSK) demodulation of the timedomain symbols.
 97. The method as claimed in claim 96, wherein the timedomain symbols are shaped by a baseband filter.
 98. The method asclaimed in claim 96, wherein the frequency domain symbols are shaped bya baseband filter.
 99. The method as claimed in claim 96, wherein eachof the plurality of complex-valued baseband symbols is spectrally shapedin one of time domain and frequency domain.
 100. The method as claimedin claim 96, wherein each of the plurality of complex-valued basebandsymbols is a π/2 BPSK DFT-spread-OFDM symbol.
 101. The method as claimedin claim 96, wherein the at least one data symbol comprises anOrthogonal Cover Code (OCC).
 102. The method as claimed in claim 96,wherein each of the plurality of complex-valued baseband symbolscomprises control information with a spreading sequence.
 103. The methodas claimed in claim 96, wherein the control information comprises anOCC.
 104. The method as claimed in claim 96, wherein each of theplurality of complex-valued baseband symbols comprises an RS based on aspreading sequence.
 105. The method as claimed in claim 96, wherein eachof the one or more receivers is associated with a different circularshifted version of the base sequence.
 106. The method as claimed inclaim 96, wherein each of the one or more receivers is associated with aspreading sequence that is orthogonal to each other spreading sequenceassociated with the one or more receivers.
 107. The method as claimed inclaim 96, wherein the RS comprises an OCC.
 108. The method as claimed inclaim 96, wherein at least one of a spreading sequence and an OCC isassociated with at least one of a receiver and an OFDM symbol number.109. The method as claimed in claim 96, wherein a receiver is associatedwith at least one of a BS specific index and a sector specific index.110. The method as claimed in claim 96, wherein a communication networksignals at least one spreading sequence and an OCC to the one or morereceivers.
 111. The method as claimed in claim 96, wherein the at leastone data symbol is filtered and the at least one RS symbol is notfiltered.
 112. The method as claimed in claim 96, wherein the at leastone RS symbol and the at least one data symbol are spectrally shapedusing the same filter.
 113. The method as claimed in claim 96, whereinthe complex-valued baseband symbols are filtered according tocoefficients that are a function of one of the three sequences [1], [11] and [0.26 0.92 0.26].
 114. The method as claimed in claim 96, whereinthe method comprises de-spreading the plurality of complex-valuedbaseband symbols according to a spreading sequence.
 115. The method asclaimed in claim 114, wherein the spreading sequence is a result ofcyclically shifting a base sequence.
 116. The method as claimed in claim96, wherein the complex-valued baseband symbols are filtered to lower apeak-to-average power ratio (PAPR).
 117. The method as claimed in claim96, wherein the complex-valued baseband symbols are shaped by a basebandfilter.
 118. A receiver, the receiver comprises: a de-multiplexorconfigured to time de-multiplex an Orthogonal Frequency DivisionMultiplexed (OFDM) waveform to generate a plurality of complex-valuedbaseband symbols comprising at least one data symbol, at least onecontrol information symbol and at least one RS symbol; a de-mapperconfigured to de-map the plurality of complex-valued baseband symbols,wherein: the at least one RS symbol is mapped according to a distributedsubcarrier mapping, the distributed subcarrier mapping comprisesoccupied subcarriers and one or more null subcarriers, the at least onedata symbol and/or the at least one control information symbol is mappedaccording to a localized subcarrier mapping, and the localizedsubcarrier mapping does not comprises a null subcarrier; an InverseDiscrete Fourier Transformer (IDFT) configured to convert frequencydomain symbols to time domain symbols using; and a demodulatorconfigured to perform π/2 Binary Phase Shift Keying (BPSK) demodulationof the time domain symbols.
 119. The receiver of claim 118, wherein abaseband filter is applied in the time domain.
 120. The receiver ofclaim 118, wherein a baseband filter is applied in the frequency domain.121. The receiver of claim 118, wherein each of the plurality ofcomplex-valued baseband symbols is spectrally shaped in one of timedomain and frequency domain.
 122. The receiver of claim 118, whereineach of the plurality of complex-valued baseband symbols is a π/2 BPSKDFT-spread-OFDM symbol.
 123. The receiver of claim 118, wherein the datasymbol comprises an Orthogonal Cover Code (OCC).
 124. The receiver ofclaim 118, wherein each of the plurality of complex-valued basebandsymbols comprises control information with a spreading sequence. 125.The receiver of claim 118, wherein the control information symbolcomprises an OCC.
 126. The receiver of claim 118, wherein each of theplurality of complex-valued baseband symbols comprises an RS based on aspreading sequence.
 127. The receiver of claim 118, wherein the receiveris associated with a unique circular shifted version of the basesequence.
 128. The receiver of claim 118, wherein the receiver isassociated with a spreading sequence that is orthogonal to each otherspreading sequence associated with one or more other receivers.
 129. Thereceiver of claim 118, wherein the RS comprises an OCC.
 130. Thereceiver of claim 118, wherein at least one of a spreading sequence andan OCC is associated with the receiver and an OFDM symbol number. 131.The receiver of claim 118, wherein the receiver is associated with atleast one of a BS specific index and a sector specific index.
 132. Thereceiver of claim 118, wherein a communication network signals at leastone spreading sequence and an OCC to the receiver.
 133. The receiver ofclaim 118, wherein the at least one data symbol is filtered and the atleast one RS symbol is not filtered.
 134. The receiver of claim 118,wherein the at least one RS symbol and the at least one data symbol arespectrally shaped using the same filter.
 135. The receiver of claim 118,wherein the complex-valued baseband symbols are filtered according tocoefficients that are a function of one of the three sequences [1], [11] and [0.26 0.92 0.26].
 136. The receiver as claimed in claim 118,wherein the receiver comprises a de-spreader operable to de-spread theplurality of complex-valued baseband symbols by a spreading sequence.137. The receiver as claimed in claim 136, wherein the spreadingsequence results from cyclically shifting a base sequence.
 138. Thereceiver as claimed in claim 118, wherein the complex-valued basebandsymbols are filtered to lower a peak-to-average power ratio (PAPR). 139.The receiver as claimed in claim 118, wherein the complex-valuedbaseband symbols are shaped by a baseband filter.